Referring to FIGS. 1 and 2, a conventional hand operated tool is shown to include a tubular casing 1, a bit operating tube 2, a cylindrical rotary bit retaining member 3, a hand grip member 7, a coupler member 4, a push rod 57 and a plurality of tool bits 6.
As illustrated, the tubular casing 1 includes a first end wall 103 which has an axis and a mounting hole 102 formed therethrough and offset from the axis, a second end wall 104, and a circumferential wall 101 that interconnects the first and second end walls 103, 104 to confine a receiving space 101C therebetween. The circumferential wall 101 is formed with a cut-out portion for access into the receiving space 101C. The second end wall 104 has a central hole 104C formed therethrough, a recess portion 104R formed in an outer surface thereof, and a pair of screw mounting posts 106 extending from an innermost wall of the recess portion 104R outwardly of the receiving space 101C. The innermost wall of the recess portion 104R further has an eccentric through hole 105 aligned with the mounting hole 102 in the first end wall 103 and in communication with the receiving space 101C.
The bit operating tube 2 has a connecting portion 202 mounted non-rotatably and securely in the mounting hole 102 of the first end wall 103, and an operating portion 201 that extends outwardly of the receiving space 101C.
The rotary bit retaining member 3 is disposed rotatably in the receiving space 101C of the tubular casing 1, and has an outer periphery 305, an axial mounting hole 301 aligned with the central hole 104C in the second end wall 104, and a plurality of axially extending bit retaining holes 302 disposed along a circular line between the mounting hole 301 and the outer periphery 305. The plurality of tool bits 6 are disposed in the bit retaining holes 302, respectively.
The coupler member 4 includes a mounting plate 401 press-fitted into the recess portion 104R of the second end wall 104, and a grip mounting portion 403 which has two lateral retention slots 404 that permit extension of the screw mounting posts 106 therethrough outwardly of the receiving space 101C. The mounting plate 401 is formed with a retention shaft 402 that extends through the central hole 104C in the second end wall 104 and the mounting hole 301 in the bit retaining member 3 to prevent removal of the bit retaining member 3 from the receiving space 101C of the tubular casing 1. Under such a condition, the bit retaining member 3 is externally accessible via the cut-out portion to rotate the same and align the tool bit 6 in a selected one of the bit retaining holes 302 with the bit operating tube 2 and the eccentric through hole 105 in the second end wall 104.
Two fastener screws 701 extend through the hand grip member 7 to engage the screw mounting posts 106 so as to mount the hand grip member 7 and the tubular casing 1. The grip member 7 has an axially extending slot 702 to slidably received the push rod 5 therein. For operating on a workpiece, the bit retaining member 3 is rotated externally to align a desired tool bit 6 with the bit operating tube 2. The push rod 5 is then pushed against the biasing action of a spring 702 toward the bit retaining member 3 so as to expose an operating tip of the desired tool bit 6 outwardly of the bit operating tube 2.
A drawback of the aforesaid hand operated tool resides in that the bit retaining member 3 is not removable from the receiving space 101C of the tubular casing 1, thereby limiting the number of assorted tool bits that can be applied thereto.
In addition, rotation of the hand grip member 7 results in corresponding rotation of the other components of the tool. As such, the tool requires a relatively large operating space, thereby making it difficult to operate in cramped spaces. Moreover, the tool requires a relatively large amount of applied force when operating on a workpiece.